1. Field of the Invention
The present invention relates to a fuel cell. More particularly, the invention relates to a planar fuel cell system.
2. Description of the Related Art
A fuel cell is a device that generates electricity from hydrogen and oxygen so as to obtain highly efficient power generation. A principal feature of the fuel cell is its capacity for direct power generation which does not undergo a stage of thermal energy or kinetic energy as in the conventional power generation. This presents such advantages as high power generation efficiency despite the small scale setup, reduced emission of nitrogen compounds and the like, and environmental friendliness on account of minimal noise or vibration. In this manner, the fuel cells are capable of efficiently utilizing chemical energy in its fuel and, as such, environmentally friendly. Fuel cells are therefore expected as an energy conversion system for the twenty-first century and have gained attention as a promising power generation system that can be used in a variety of applications including space applications, automobiles, mobile devices, and large and small scale power generation. Serious technical efforts are being made to develop practical fuel cells.
In particular, polymer electrolyte fuel cells feature lower operating temperature and higher output density than the other types of fuel cells. In recent years, therefore, the polymer electrolyte fuel cells have been emerging as a promising power source for mobile devices such as cell phones, notebook-size personal computers, PDAs, MP3 players, digital cameras, electronic dictionaries or electronic books. Well known as the polymer electrolyte fuel cells for mobile devices are planar fuel cells, which have a plurality of single cells arranged in a plane.
With a planar fuel cell, the electric power depends on the total area of electrodes. On the other hand, the voltage depends on the number of cells connected in series. Accordingly, in order to downsize the fuel cell and obtain necessary power and voltage, the number of cells connected in series within a limited area needs to be increased and the area of each cell needs to be made smaller. At the same time, the spacing between adjacent single cells needs to be shortened.
The cell pitch is desirable to be made smaller in order to reduce the resistive electrical losses from edge collection of electrical current. Increasing the number of fuel cells will in general reduce ohmic losses but will also reduce the total active area of the planar array due to the space overhead of the interconnect between neighbouring fuel cells. An objective of this invention is to facilitate designs and methods that can serve to decrease the size of the fuel cell interconnect regions in a planar array.